The present invention relates to a method for manufacturing a contact terminal that slides against a contact plate, an apparatus for manufacturing a contact terminal, and a contact terminal.
A motor used as a drive source for a vehicle wiper device includes a motor unit and a reduction gear unit, which are coupled integrally with each other. The motor unit rotates and drives a rotation shaft when supplied with power. The reduction gear unit reduces the speed of the rotation generated by the motor unit. The reduction gear unit accommodates a worm wheel, which forms a reduction gear mechanism, and an output shaft, which rotates integrally with the worm wheel. A link mechanism connects the output shaft to a wiper.
In such a motor, when a wiper switch is deactivated to stop the wiping action of the wiper, the wiper continues to move until reaching a predetermined stop position before stopping. To supply power to the motor unit in accordance with the position of the wiper, that is, the rotational position of the output shaft, the motor includes a rotation plate, which is used to detect the rotational position of the output shaft, and a plurality of contact terminals, which slide against the rotation plate (refer to, for example, Japanese Laid-Open Utility Model Publication No. 55-56753). A conductive plate undergoes a punching process to obtain a contact plate having a predetermined conductive pattern. The contact plate is then fixed to a holding member made of an insulating material. This forms the rotation plate, which is disk-shaped. The contact terminals are conductive and strip-shaped. Each contact terminal includes a distal part that defines a contact portion projecting in a thicknesswise direction of the contact terminal. Further, each contact terminal includes a basal part fixed to the interior of the motor. The contact portion of each contact terminal is in contact with and slidable against the surface of the rotation plate, which includes the surface of the holding member and the surface of the contact plate. In the motor, the detection of the rotational position of the output shaft and switching are performed based on the contact position of each contact terminal relative to the rotation plate.
As described in Japanese Laid-Open Patent Publication No. 2002-81905 (FIGS. 3 and 12), a pressing (drawing) process may be performed to form the contact portion of each contact terminal. Alternatively, a pin-shaped contact member, which is a discrete member, may be inserted through and fixed to a distal part of a strip-shaped metal plate, which forms a contact terminal, to use the contact member as a contact portion.
The contact portion of each contact terminal slides against the surface of the rotation plate when the rotation plate rotates and passes by the boundary between the contact plate and the holding member from the surface of the contact plate to the surface of the holding member. In this case, an increase in the contact area between the contact portion and the surface of the rotation plate increases the time required from when the contact portion reaches the boundary to when the contact portion completely passes by the boundary. This decreases the detection accuracy of the rotational position of the output shaft and the switching position accuracy. To increase the accuracy, it is desirable that the state of conduction between the contact portion and the rotation plate be quickly switched. To quickly switch the state of conduction, it is desirable that the distal part of the contact portion be thinly formed.
Further, at the boundary between the contact plate and the holding member, contact of the contact portion with a corner at an edge of the contact plate may cause abrasion when the state of conduction switches in addition to abrasion caused by sliding of the contact plate. Thus, in addition to having a thin distal part, it is desirable that the contact portion be formed to have sufficient height (length).
When a pressing process is performed to form the contact portions, the contact terminals including the contact portions can be formed from the same metal plate. This lowers the cost for forming the contact terminals. However, the contact terminals are small. Thus, when forming each contact terminal with a thin distal part and a contact portion having an increased height, cracks may form during the pressing process, especially, at the contact portion.
A contact terminal including a thin distal part and a contact portion having an increased height can be formed by fixing the discrete pin-shaped contact portion to the metal plate. However, this requires the contact member in addition to the metal plate. Further, in addition to performing a pressing process on the metal plate in accordance with the shape of the contact terminal, a process for fixing the contact member to the metal plate is performed. This increases manufacturing costs.